4-(Diphenylmethyl)-1-piperidinemethanimine (1) is a potent oral gastric antisecretory agent in rats but contains a strong anticholinergic component. Since a nonanticholinergic gastric antisecretory drug would be useful in the treatment of peptic ulcer disease, a program was initiated by us to find such an agent based on 1. Compound 1 contains structural elements common to the anticholinergics atropine and homatropine. Studies on the structure-activity relationships of these compounds and their derivatives have revealed certain modifications that diminish or abolish anticholinergic activity. The application of these modifications to the design of analogues of 1 afforded an antisecretory compound, 4-(diphenylmethyl)-1-[(octylimino)methyl]piperidine (3h, fenoctimine), which exhibited no anticholinergic activity. Fenoctimine is undergoing clinical trial as a gastric antisecretory drug.